In general, optical components for switching or attenuating selected channels in wavelength division multiplexed (WDM) systems are useful in optical network elements, such as reconfigurable optical add-drop multiplexers (ROADMs). A spatial dispersion module is typically employed in such devices for spatially dispersing optical signals and projecting the spatially dispersed optical signals on a spatial light modulator.
A spatial light modulator for wavelength division multiplexing (WDM) applications is typically comprised of a one-dimensional pixel array for modulating incident optical signals, where each pixel is assigned to a different wavelength channel and the operation of each pixel varies according to the application of the spatial light modulator. For example, a pixel may attenuate an optical signal (e.g., for an optical channel blocker) or switch an optical signal between optical fibers (e.g., for a wavelength selective switch).
In existing spatial light modulators, the one-dimensional pixel array is configured such that there is a finite pixel gap between each pair of adjacent pixels in the one-dimensional pixel array. Furthermore, the one-dimensional pixel array is configured such that each pixel in the one-dimensional pixel array has an associated pixel pitch that matches the system channel spacing (e.g., 100 GHz).
Disadvantageously, however, pixel gaps between pixels in the pixel array produce spectral transmission dips. As such, optical transmission systems utilizing dynamic bandwidth allocation would incur substantial transmission penalties from such spectral transmission dips. Specifically, any signal component present at the location of an inter-pixel gap is distorted from the cumulative effects of amplitude and phase variations at the resulting transmission drops.